1. Field of the Invention
The present invention relates generally to crank and slide presses for manufacturing metal containers. More particularly, the present invention relates to apparatus and method for aligning the redraw die and the ironing dies with a redraw punch that is attached to a body maker ram.
2. Description of the Related Art
Crank and slide presses are used for punching, shearing, drawing, and redrawing operations in manufacturing articles from metallic sheets or rolls of metallic strip material. In general, a crank and slide press includes a crank that is mounted for rotary motion, an electric motor that is connected to the crank that imparts rotary motion thereto, a connecting rod that is attached to the crank, and mechanism for changing motion from the connecting rod to rectilinear reciprocating motion. A more detailed description of crank and slide presses is given by Maytag in U.S. Pat. No. 3,696,657, issued Oct. 10, 1972.
One specific use for a crank and slide press is in the production of beverage cans. A redraw cup is drawn from a coiled strip by a first crank and slide press, and then the redraw cup is redrawn on a second crank and slide press forcing the redraw cup through a tool pack subassembly that includes a redraw die and a plurality of ironing dies.
In the highly competitive container industry, a container must be made with the absolute minimum of material, which means that the finished container must have extremely thin walls. It should be apparent that the use of extremely thin walls of the finished containers places stringent concentricity requirements on the walls of the container, and thereby on concentricity of the redraw die and ironing dies with the redraw punch.
More particularly, it is highly desirable to maintain concentricity of the redraw die and ironing dies to the redraw punch, to less than 0.0003 inches (0.00762 mm); and it is imperative that maximum wall thickness variations be kept to less than 0.001 inches (0.0254 mm).
Further, because of the competitiveness of the container industry, the speed of the press must be maximized and downtime of the press must be minimized. As should be apparent, maximizing speed and minimizing downtime are inherently opposite, because higher speeds impose higher stresses on the machinery and cause higher wear rates.
In the redraw operation, a tool pack subassembly, with the redraw die and a plurality of ironing dies therein, is mounted circumferentially around the longitudinal machine axis wherein the body maker ram is reciprocated; a redraw punch is attached to the body maker ram and is reciprocated towards, into, and through the tool pack subassembly, including both the redraw die and the ironing dies thereof; and the redraw punch is withdrawn from the tool pack subassembly and all of the parts thereof.
A redraw cup is positioned against the redraw die and is resiliently held against the redraw die by a redraw sleeve, the redraw sleeve is attached to a redraw carriage, and the redraw carriage is reciprocated toward and away from the redraw die.
The redraw sleeve serves two functions. One function of the redraw sleeve is to assure concentricity between the redraw cup and the redraw die. The other function of the redraw sleeve is to provide resilient clamping between a clamping face of the redraw sleeve, the redraw cup, and the redraw die, thereby preventing wrinkling of the metal as the redraw cup is redrawn through the redraw die.
Because of stringent alignment requirements, the redraw die must be aligned with the redraw punch, and then each of the ironing dies must be separately aligned with the redraw punch.
In a typical tool pack subassembly, each of the dies in the tool pack are positioned by two wedges each which provides adjustment along one of two transverse and intersecting axes, and by an air cylinder that resiliently forces that die against the aforementioned adjusting wedges. Each of the wedges is selectively positioned by loosening two locknuts, turning an adjusting screw, and locking the two locknuts.
In the prior art, a die alignment system has been used in which four magnetic position transducers, two along each of two transverse and intersecting axes, have been used. Each transducer senses the relative distance to the redraw punch, and so the readout of the transducers must be balanced to provide a readout that indicates eccentricity of a given die to the redraw punch.
In contrast to the prior art, the present invention provides die alignment and method in which two mechanical-contact transducers, one for each of two transverse and intersecting axes, are used, and in which the transducers are precalibrated on a calibrating fixture, thereby providing an absolute, rather than a relative, readout.
In a first aspect of the present invention, a method is provided for aligning a body maker die with a redraw punch in a crank and slide press having a body maker ram adapted for attachment of the redraw punch thereto and having a tool pack with a plurality of die slots therein, which method includes disposing first and second position transducers in an alignment die along respective ones of first and second transducer axes that are orthogonal to each other and to a longitudinal reference axis; calibrating the readout of the transducers with respect to first and second calibration dimensions; placing the alignment die in the tool pack with the longitudinal reference axis parallel to a longitudinal machine axis of the body maker ram; attaching an alignment punch to the body maker ram; inserting the alignment punch into the alignment die; taking measurements along the first and second transducer axes; and positioning the alignment die along X and Y axes that are orthogonal to each other and to the longitudinal machine axis.
In a second aspect of the present invention, a method is provided for aligning a body maker die with a redraw punch in a crank and slide press having a body maker ram adapted for attachment of the redraw punch thereto and having a tool pack with a plurality of die slots therein, which method includes disposing a first position transducer and a second position transducer in an alignment die; placing the alignment die into a calibration fixture with a calibration surface; calibrating the first and second position transducers against the calibration surface; inserting the alignment die in one of the die slots of the tool pack; and positioning the alignment die along X and Y axes.
In a third aspect of the present invention, a method is provided for aligning a body maker die with a redraw punch in a crank and slide press having a body maker ram adapted for attachment of a redraw punch thereto and having a tool pack with a plurality of die slots therein, which method includes disposing first and second position transducers along first and second transducer axes in an alignment die; disposing the alignment die around a calibration surface; radially positioning the alignment die by contacting a locating surface thereof that is disposed radially outward of the alignment die; zeroing the readout of the transducers with respect to the calibration surface; disposing the alignment die in one of the die slots; positioning the alignment die by contact with the locating surface thereof; and positioning the alignment die along X and Y axes in accordance with the calibrating step.
In a fourth aspect of the present invention, a die alignment apparatus is provided for aligning a body maker die with a redraw punch in a crank and slide press having a body maker ram adapted for attachment of the redraw punch thereto and having a tool pack with a plurality of die slots therein, which alignment apparatus includes a base having a surface; a calibration punch being disposed around a longitudinal calibration axis that is orthogonal to the surface of the base, being attached to the base, and having a calibration surface that extends orthogonally from the surface of the base; an alignment die having an outer surface, and having an opening therethrough that is removably disposed over the calibration punch; locator means, comprising spaced-apart locator pins that are attached to the base, for locating the alignment die by contact with the outer surface; and transducer means, comprising first and second position transducers that are operatively attached to the alignment die, for taking measurements with respect to the calibration surface.
In a fifth aspect of the present invention, a die alignment apparatus is provided for aligning a body maker die with a redraw punch in a crank and slide press having a body maker ram adapted for attachment of the redraw punch thereto and having a tool pack with a plurality of die slots therein, which alignment apparatus includes an alignment die having inner and outer surfaces that are disposed circumferentially around a longitudinal reference axis, and having first and second position transducers that are disposed along respective ones of first and second transducer axes that are orthogonal to the longitudinal reference axis and to each other; and a calibration fixture having locator means for locating the alignment die by contact with the outer surface of the alignment die, and having calibration surface means for calibrating the position transducers.